Hemocytes of saturniid silkworms: Their behavior in vivo and in vitro in response to diapause, development, and injury

The blood of the wild silkworms Antheraea polyphemus, Samia cynthia, and Hyalophora cecropia (Lepidoptera; Saturniidae) contains two predominant classes of hemocytes, plasmatocytes and granulocytes, which are markedly different in their behavior. In diapausing pupae or developing adults, both types occur in nearly equal numbers. Following surgical injury there is a dramatic increase in the population of plasmatocytes. The behavior of the cells in vitro is not related to their origin but depends on the conditions of culture. In hanging drops the plasmatocytes clump together. On glass or plastic surfaces they become flattened and, like vertebrate fibroblasts, migrate apart to cover the surface with a sheet of cells. Identical cellular membranes from in vivo at wound sites. When dissociated fat‐body cells or tiny beads of resin are cultured in blood, the plasmatocytes adhere to them and draw them into large, heterogeneous aggregates. The granulocytes are completely passive in vitro under all conditions.